Interpretive Summary: Over the last 10,000 years, crop domestication has been the single most important human cultural development. Grasses are prominent among these crops, and provide the vast majority of the world's food. Similar traits have been selected during their domestication and breeding, and since these critically important grasses share a similar complement of genes, the same set of genes may be have been selected. Even though the process of domestication of these grasses occurred over the same 5000 to 10,000 year period, the domesticated grasses have major differences in genome structure, diversity, and life history. We discuss our present knowledge of molecular diversity among the grass crops and relate that diversity to the genes involved in domestication and to yield gains. A domestication model of the small drops in crop diversity is developed. Understanding this connection between diversity and genome structure will be critical to future efficient crop breeding.

Technical Abstract:
We discuss how genetic diversity and genome structure are related to increases in grass crop yields since domestication. First, we establish that most of the domesticated grasses have about two-thirds of the diversity of their wild progenitors. Second, we developed a model of domestication to explain this modest drop in diversity across the grasses. Finally, we also demonstrate that both gene duplication and diversity have played important roles in increasing yield in the grasses, however, the relative importance is difficult to assess. A novel sampling scheme that includes survey of domestication failures may elucidate this problem.